Posted
by
samzenpus
on Thursday August 21, 2014 @04:30AM
from the new-way-of-thinking dept.

StartsWithABang writes It's the holy grail of modern particle physics: discovering the first smoking-gun, direct evidence for physics beyond the Standard Model. Sure, there are unanswered questions and unsolved puzzles, ranging from dark matter to the hierarchy problem to the strong-CP problem, but there's no experimental result clubbing us over the head that can't be explained with standard particle physics. That is, the physics of the Standard Model in the framework of quantum field theory. Or is there? Take a look at the evidence from the muon's magnetic moment, and see what might be the future of physics.

I'm a bit biased, but consider finding non-zero neutrino mass (via neutrino oscillations) as the first "beyond the standard model" evidence. Slashdot carried that story in its infancy, way back in 1998.

Also worth pointing out that TFA is talking about an experiment in construction that hopes to push the g-2 result past 5 sigma. It's not there yet, although 4.something sigma is still pretty darn good. Just 14 years late to the party.

Gravity can be formulated as a gauge theory, like the other forces in Standard Model. It's just a different mathematical representation of General Relativity, and it also captures the gravity-as-curvature idea quite neatly. You don't see it that often because the math gets a little tricky, unless you use something like Geometric Algebra [cam.ac.uk], which made it easy enough for Master's courses.

Actually, the good news is that the experiment is definitely happening! They moved the ring to Fermilab last year and are busy setting it up to run. You can read more about it here: Muon g-2 at Fermilab [fnal.gov]. They even have a Facebook page [facebook.com].

As someone who has not been involved in neutrino physics (at least until very recently) I'd agree that neutrino oscillations are the first physics discovered that is beyond the Standard Model. In addition even if the g-2 experiment gives a 5 sigma discrepancy it tells you very little about what any possible new physics - to do that you have to produce the new particles directly and study them.

The corrections to the muon g-2 experiment are now so high order that they involve QCD loops. These are non-perturbative and incredibly hard to calculate correctly so all a 5 sigma discrepancy may mean is that the theorists have got the calculation wrong. Indeed this has happened before with a 3 sigma g-2 'signal' going away after an error in the theory calculation was found by the student of one of my departmental colleagues.

If I show my bias then I would say that the best chance of new physics is the new LHC run starting in March 2015 where we have almost twice the energy of the previous run and higher luminosity. This should at least double the reach of the LHC for new physics over the next 3 years. After this run any sensitivity gains to new physics will come from increasing luminosity and so take far longer to achieve, perhaps giving one more doubling of the reach but over the next ~15 years and with a lot of work involved since the high luminosity LHC upgrade has incredible background rates!